Oil and gas drilling rigs frequently support a rotating drill pipe with a swivel or top drive anchored to a derrick. The swivel or top drive provides support for the rotating pipe and provides a sealed joint between fixed portions of the rig and rotating portions of the pipe. The top drive or swivel may include a suspended gear box that allows drill pipe extending out the bottom of the swivel to be rotated. Alternately a kelly drive and rotary table may be used.
Drilling fluid, such as mud or air, passes through a top portion of the swivel, referred to as a “gooseneck,” and down through the rotating pipe. With such swivel or top drive, the fluid or air passes through a tube, referred to as a “washpipe,” that sealingly mates with a portion of the rotating drill pipe at a seal or packing assembly. Either the seal or the washpipe rotates with the pipe; the other remains stationary.
A swivel is typically anchored to a derrick frame so that the swivel's motion itself is limited to the vertical direction. A power swivel typically carries a motor for turning the drill pipe and mates with the gooseneck or hose or line for communicating drilling fluid from a fluid reservoir to the open top end of the rotating drill pipe. The drilling fluid may be under pressures up to 5,000 to 7,000 psi and temperatures up to 200 degrees Fahrenheit as it flows from the gooseneck through the swivel or top drive containing the washpipe and to the drilling pipe suspended for rotation.
To provide sealing mating between fixed swivel portions and rotating drill pipe, while pumping drilling fluid down the rotating drill pipe, the drilling fluid potentially under high temperature and pressure, the swivel carries a carefully machined washpipe and packing assembly. Typically the washpipe is stationary with the top of the washpipe sealingly connecting, directly or indirectly, with the bottom of the gooseneck and the bottom of the stationary washpipe sealingly connecting, via a rotating packing assembly, to rotating drill pipe. The rotating packing assembly provides a rotating seal SL, FIG. 1, for mating with a smoothly coated surface of a stationary washpipe. The rotating seal SL, FIG. 1, typically comprises a series of vertically stacked packing ring seals (made of a pliable material) which rotate about the circumference of the stationary washpipe tube, maintaining a fluid tight seal even under high pressure and temperature conditions.
To maintain the rotating seal under the high pressures and temperatures demanded in some operations with drilling fluids, the packing assembly must be frequently lubricated. Although the washpipe is structured (milled, ground, coated) for sealing with a rotating packing assembly at its lower end, sufficient friction is generated, taking into account that the joint must continue to seal against high pressure and temperature, that the packing assembly must be lubricated several times a day.
Typically a packing assembly is lubricated at least twice a day. The purpose of adding lubricant media to the packing rings can be twofold, to “energize” the packing rings to insure that a seal lip continues to stay in contact with the washpipe tube and to provide a boundary lubricant film between the seal lip and the washpipe tube to reduce friction and thereby increase seal effectiveness and life cycle. Lubricating a packing assembly in normal conditions requires stopping the rotating operation at set time intervals so that the lubricant can be injected at the packing assembly lubrication point. Current art techniques for lubrication require the drilling to be suspended and the packing assembly to be held stationary for 15 to 30 minutes while the lubricant is manually inserted through a portion of the outer wall of the packing assembly. This requires at least one person to ascend the derrick. Harsh conditions (high rotational and extreme high pressure) may require an even shortened service interval due to elevated friction between the seal lips and the washpipe.
The standard lubrication operation typically requires the efforts of three men, one of whom is required to climb the derrick. Such operations involve a certain amount of risk for the personnel as well as downtime.
The objective in developing the instant “sleeved” washpipe is to address at least one of three major goals: 1) reduce the hazard and risk to personnel by eliminating a need for frequent manual maintenance of the seal lubrication; 2) increase the life cycle of the washpipe and seals by providing a better thermal and pressure protection to the washpipe tube via added wall thickness (the internal sleeve) and precise lubrication at exact intervals as dictated by the end user via an adjustable control system; and 3) save the end user time and money by eliminating the need to stop operations for periodic maintenance of the washpipe stuffing box seals.
Preferred embodiments of the instant invention provide for ports in the washpipe, at least one port communicating through the washpipe at an exterior portion of the washpipe outside of the packing assembly/washpipe interface area and at least one other port communicating through the washpipe tube within the packing assembly/washpipe interface area. The invention further preferably provides a communication channel, at least in part by cooperation with a washpipe liner, such that lubricant can be inserted into at least one first port and transmitted to at least one second port, and thence to a packing assembly/washpipe interface area, preferably semi or fully automatically, without a human having to climb a derrick. Potentially, lubrication can be performed while drilling.
Preferably, the communication channel is provided by means of a channel in or between an exterior portion of a sleeve preferably having an interference fit with the interior of the washpipe and an interior portion of the washpipe. The channel should register for fluid communication with the washpipe ports. The channel could be accommodated by altering portions of the washpipe.
Preferably, the sleeve is comprised of a plastic that has characteristics of (1) toughness under high temperature and pressure; (2) resistance to erosion and cracking from drilling fluid, and (3) a capacity to shrink when cooled and re-expand at ambient temperature in order to maintain a high temperature, high pressure seal so as to neither leak nor be eroded nor be cracked by abrasion from the drilling fluid. The interior sleeve could be comprised of a stainless steel for some embodiments and pressure/temperature ranges.